Unitary wound resistor-capacitor network

ABSTRACT

Two network forming strips are wound to form a resistorcapacitor network roll. Each strip is a sheet of dielectric material having a contiguous layer of metal, on one side thereof, formed in an elongated conductive path which extends back and forth lengthwise along the strip in serpentine fashion. An electrical connection is made at each end of the network roll with an end portion of a different one of the conductive paths to form an R-C network therebetween having a resistance which is significant with respect to the capacitance thereof.

United States Patent Brown et al.

[ Jan. 15, 1974 1 UNITARY WOUND RESISTOR-CAPACITOR NETWORK I [75] Inventors: Donald R. Brown, Downers Grove;

Otto I. Masopust, Jr., Claredon Hills; James F. Stoltz, LaGrange, all of I11.

[73] Assignee: Western Electric Company,

Incorporated, New York, NY.

[22] Filed: Nov. 16, I972 [211 Appl. No.: 307,072

[52] US. Cl 317/256, 323/78, 333/79, 338/300, 338/334 [51] Int. Cl ..I-l01g 1/00 [58] Field of Search 317/242, 260, 256, 317/258, 261; 333/79; 323/78, 74; 338/300, 296, 334

[56] References Cited 7 UNITED STATES PATENTS 2,216,558 10/1940 Ortlieb 317/242 2,448,513 9/1948 Brennan... 317/258 X 2,915,808 12/1959 Clemons 317/260 X 2,921,246 1/1960 Peck 317/260 FOREIGN PATENTS OR APPLICATIONS 1909 Great Britain 317/261 OTHER PUBLICATIONS Dummer et a1., Fixed & Variable Capacitors",

McGraw Hill, N.Y., 1960, p. 89.

Primary ExaminerE. A. Goldberg A tt0rney- R. 1. Lloyd [57] ABSTRACT Two network forming strips are wound to form a resistor-capacitor network roll. Each strip is a sheet of dielectric material having a contiguous layer of metal, on one side thereof, formed in an elongated conductive path which extends back and forth lengthwise along the strip in serpentine fashion. An electrical connection is made at each end of the network roll with an end portion of a different one of the conductive paths to form an RC network therebetween having a resistance which is significant with respect to the capacitance thereof.

5 Claims, 5 Drawing Figures UNI'IARY WOUND RESISTOR-CAPACITOR NETWORK BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to unitary resistorcapacitor networks and to methods of fabricating such networks, and in particular to a unitary wound,.metallized-coated dielectric type of resistor-capacitor network roll wherein the metal coating on the dielectric is a relay coil so that when contacts in the coil circuit open, to deenerize the coil, the network absorbs and dissipates the energy in thecollapsing field of the coil to prevent an excessive voltage rise at the contacts which, if unchecked, would lead to arcing. Alternatively, the network may be connected directly across the contacts, and in this case upon opening of the contacts the network operates to shunt the energy in the collapsing coil field around the contacts until the gap between the contacts becomes sufficiently large to preclude arcing.

In fabricating relay coils for use in electronic circuits, the coil is often packaged within a metal container, or can, to shield the electronic circuit employing the coil from radio interference caused by the collapsing field of the coil. If an R-C network is to be connected across the windings of the relay coil, it is convenient to package the network within the metal container with the relay coil so that the coil and network form a single, or one piece, elecronic component. In such a case, it is desirable to employ an RC network having a minimum physical size to both facilitate the connection of the network acrossthe windings of the coil, which are normally presented between two closely spaced terminals in the base of the coil, and to minimize the size of the metal container required to package both the coil and the network.

One type of presently employed R'-C network having asmall physical size is aunitary wound R-C network of the metal coated paper or of the metal coated plastic film variety, which is similar in construction to rolled metal coated paper capacitors and to rolled metal coated plastic film capacitors. The resistance and capacitance of such networks is obtained by connecting electrical contacts to the ends of the metal coatings instead of to a maximum area of one side of each of the coatings as for pure capacitors. For such networks, the contacts with the metal coatings are normally achieved with laid-in terminals; that is, with terminals laid across the far extremities of the metal coatings. Such contacts, however, electrically engage only a very small area of the thin metal coatings and are often burned away when the network is subjected tohigh current pulses, resulting in an open circuit and a useless network.

A further disadvantage of such networks is that the resistance of the network is small in comparison with the capacitance of the network. This occurs because the capacitance of the network is a function of the total overlapping areas of the metal layers thereof and of the properties of the dielectric layers therebetween, while the resistance of the network is a function of the length and of the resistance per unit of length of the metal layers. With conventional networks, the resistance per unit of length of the metal layers is normally small since the conductive path extends across the entire width of the metal layer, and the length of the metal layer is normally short since the length is dependent upon the capacitance value desired.

SUMMARY OF THE INVENTION In accordance with the present invention, a network is fabricated by forming a first conductive path contiguous to one side of a first sheet of insulating material and a second conductive path contiguous to one side of a second sheet of insulating material. Each conductive path extends back and forth lengthwise along its associated sheet in a serpentine fashion. The sheets of insulating material and the conductive paths are then rolled into convolutions with the first sheet of insulating material spaced between the first and the second conductive paths, and an electrical termination is placed in contact with an end portion of each of the conductive paths.

Preferably, a resistor-capacitor network having a resistance value R and a capacitance value C is fabricated from first and second network forming strips, eachstrip being a sheet of dielectric material having a conductive, metal layer contiguous to one side thereof, by first providing a length of each. of the network forming strips which is equal to that required, when the strips are overlapped and when taken in conjunction with the width of the metal layers of the strips and the properties of the dielectric material thereof, to form an unrolled capacitor having the capacitance value C/2. The metal layer on each of the network forming strips is then removed along a plurality of spaced lines which extend essentially parallel to the length of the strip, with alternate lines beginning at a first end of the metal layer and terminating before reaching a second and opposite end of the metal layer, and with the remaining lines beginning beyond the first end of the metal layer and terminating at the second end of the metal layer. This forms with the remaining metal layer on each of the strips a conductive path which extends back and forth lengthwise along the strip in a serpentine fashion and which exhibits a resistance value of R between its ends. The first and second network forming strips are then overlapped, such that the dielectric material of one of the strips is spaced between the metal layer of that strip and the metal layer of the other strip, and the overlapping strips are rolled into convolutions to form a network roll. An electrical contact is then formed on an end portion of each of the conductive paths. The networkso fabricated exhibits a resistance value of R and a capacitance value essentially equal to C in response to an energizing signal applied across the contacted portions.

Other objects, advantages and features of the invention will be apparent upon consideration of the following detailed description when taken in conjunction with the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the configuration of conductive paths on each of two sheets of dielectric material employed in fabricating an R-C network in accordance with the present invention;

FIG. 2 is a partial front view of an apparatus for fabricating R-C networks in accordance with the present invention;

FIG. 3 shows the structure of an R-C network as fabricated with the apparatus of FIG. 2;

FIG. 4 is a perspective view of an R-C network having electrical connections made therewith, and

FIG. 5 is the electrical circuit equivalent of the network shown in FIG. 4.

DETAILED DESCRIPTION The R-C network of the present invention includes, as shown in FIG. 1, two network forming strips 12 and 16, the strip 12 including a sheet of dielectric material having a contiguous and conductive metal layer 24 on one side thereof, and the strip 16 including a sheet of dielectric material 28 having a contiguous and conductive metal layer 32 on one side thereof. The dielectric sheets 20 and 28 may be of paper or plastic such as polycarbonate, polystyrene or polyester sold under the name Mylar; however, any flexible dielectric material may be used. The metal layers 24 and 32 may be of any conductive material such as aluminum, silver, zinc or alloys thereof. Preferably, the conductive metal layers 24 and 32 are positioned contiguous to their respective sheets of dielectric material by coating one side of the sheets using metal vapor deposition or sputtering techniques, and are considered'as being so positioned in the description of the invention. However, the metal layers may also be positioned contiguous to the dielectric sheets by placing a strip of metal foil next to the sheet without bonding the surfaces together.

Normally, the resistance across the width of each of the metal layers 24 and 32 is small. To increase the resistance across the width of the metal layers, the metal layer on each of the network forming strips 12 and 16 is removed along a plurality of straight, spaced lines which extend essentially parallel to the length of the strips. As shown, each metal layer has been removed along a first plurality of alternate narrow lanes or lines 36 which begin at a first end 40 of each of the metal layers 24 and 32 and end before reaching a second and opposite end 48 of the metal layers. Additionally, the metal layer on each of the network forming strips has been removed along a second plurality of alternate lanes or lines 44 from a position beginning beyond the first end 40 of each of the metal layers 24 and 32 and ending at the second end 48 of each of the metal layers. In this manner, the remaining metal layer on each of the network forming strips forms, or is configured in, a conductive path extending back and forth lengthwise along the strip in a serpentine fashion. The metal layer 24 on the strip 12 forms a serpentine path beginning along a first lengthwise edge 52 of the network forming strip 12 and ending along an uncoated area, or margin 56, on the dielectric material 20 adjacent a second lengthwise edge 60 of the strip 12, and the metal layer 32 on the strip 16 forms a serpentine path beginning along a first lengthwise edge 64 of the network forming strip 16 and ending along an uncoated area, or margin 68, on the dielectric material 28 adjacent a second lengthwise edge 72 of the strip 16.

That the resistance across the width of the network forming strips and through the metal layers, extending back and forth lengthwise and across the width of each of the network forming strips 12 and 16, has been increased by the removal of the metal layers along the lines 36 and 44 is obvious. The resistance R through the conductive path formed by the metal layers is equal to pL/wt, where p is the resistivity of the metal layer in ohm-meters, L is the length of the conductive path in meters, w is the width of the conductive path in meters, and t is the thickness of the conductive path in meters. By the formation of the serpentine path in the metal layers, the length L of the conductive path formed by each metal layer has been increased while the width w of the path has been decreased. From the relationship R pL/wt, if L is increased and w is decreased, while p and t remain constant, then R must increase.

Preferably, the lanes or lines 36 and 44 of removed metal layer are very narrow, so that the surface area of the metal layers is not appreciably reduced. In this manner, if the network forming strips 12 and 16 are overlapped with the dielectric material of one of the strips spaced between the metal layer of that strip and the metal layer of the other strip, the capacitance exhibited between the metal layers is essentially equal to the capacitance which would be exhibited if the lines of metal layer had not been removed, and a minimum length of network forming strips is required to obtain a desired capacitance value.

To form a network roll, lengths of the network forming strips 12 and 16 are convoluted, or wound together, with an apparatus of the type shown in FIG. 2. A supply of the network forming strip 12, not having any portions of the metal layer thereof removed, is maintained on a rotatable reel 76 and extends from the reel around a guide roller 80, around a nonconductive guide roller 84, between two nonconductive guide rollers 88 and 92, and to an arbor 96. Similarly, a supply of the network forming strip 16, also not having any portions of the metal layer thereof removed, is maintained on a rotatable reel and extends from the reel around a non-conductive guide roller 104, around a guide roller 108, between the two guide rollers 88 and 92, and to the arbor 96. At the arbor 96, which winds, or convolutes, the network forming strips 12 and 16 together to form a network roll, the strips are overlapped with the dielectric material of one of the strips positioned between the metal layer of that strip and the metal layer of the other strip to electrically isolate the two metal layers 24 and 32, as electrical contact between the metal layer of one of the strips and the metal layer of the other strip would destroy the usefulness of the network. As shown in FIG. 3, to insure against accidental electrical contact between the two metal layers 24 and 32 and to facilitate, as will be later explained, an electrical connection with the metal layer of the network forming strips, the overlapped network forming strips 12 and 16 are slightly offset with respect to each other with the margin 56 of the strip 12 overlying the metal coating 32 of the strip 16 and with the margin 68 of the strip 16 overlying the metal coating 24 of the srip 12.

To remove the metal layer along lanes or lines extending lengthwise along the strips 12 and 16, a metal removing device 112 associated with the network forming strip 12, and a metal removing device 116 associated with the network forming strip 16, which devices may be either lasers or electron discharge devices having sufficient power to cut through and remove the metal layer, are each positioned to project one or more narrow energy beams onto the metal layer of their associated strip. Alternatively, the devices 112 and 116 may be mechanical cutters, each positioned to sever, or remove metal from, its associated metal layer along one or more lines. As the network forming strips are wound together on the arbor 96 and advanced past the metal removing devices 112 and 116, the devices remove metal therefrom to form one or more longitudinal lines of removed metal in each of the metal layers. Each of the devices 112 and 116 may be a plurality of laser or electron discharge devices, or a plurality of mechanical cutters, which are individually actuable to remove metal from the metal layers along lines having a selected configuration. That is, the devices 112 and 116 are selectively actuable to remove the metal layer along alternate lines on each of the network forming strips 12 and 16 from a position beginning at the first end 40 of the strips and ending before the second end 48 of the strips, and to remove the metal layer from the remaining alternate lines from an initial position beginning beyond the first end 40 of the strips and ending at the second end 48 of the strips. That is, the devices 112 and 116 are actuable to remove the metal layer along odd numbered lines, as numbered from a first lengthwise edge of each strip, from a position beginning at a first end of the metal layer and terminating before reaching a second, and opposite, end of the metal layer, and to remove the metal layer along the even numbered lines, as numbered from the first lengthwise edge of each strip, from a position beginning beyond the first end of the metal layer and terminating at the second end of the metal layer. g A

After the network roll has been wound on the arbor 96, an electrical connection is provided at each end of the network roll to an end portion of a different one of the metal layers of the network forming strips by two solderblocks 120 and-124, the solder block 120 electrically engaging an end portion of the metal coating 32 along the lengthwise edge 64 of the network forming strip 16 arid the solder block 124 electrically engaging an end portion of the metal coating 24 along the length wiseedge 52 of the network forming strip 12. The solder blocks may be sprayed, in the molten state, onto each of the network ends by conventional solder spraying apparatus (not shown). The positioning of the margins 56 and 68 and the offset of the network forming strips 12 and 16, as shown in FIG. 3, presents at each end of the network roll a differentone, and only one, of the metal layers 24 or 32, and facilitates electrical engagement between the solder and the edge of a different metal layerat each end of the network roll without electrically shorting the two metal coatings together. Lead connections are made to each of the solder blocks 120 and 124 by conductors 128 and 132, respectively.

Each of the solder blocks 120 and 124 electrically contacts the edge of a different one of the metal layers 24 and 32 along a length which is substantially equal to the total length of the network forming strips. This differs from the contacts provided to present R-C networks wherein only a very small area at an end of each of the metal coatings is contacted. By electrically contacting an appreciable length of the edge of each of the thin metal layers a current carrying connection, which is not readily subject to being burned away, is provided to the network of the invention. The electrical equivalent of the complete network roll, as shown in FIG. 4,

is shown in FIG. 5, and is a capacitor connected in se' ries with a resistor, both of which are formed by the lengths of the overlapping metal coatings 24 and 32 between the solder blocks and 124. The resulting network roll or circuit, as fabricated, forms an R-C network having a resistance which is significant with respect to the capacitance. As already stated, this occurs because the resistance of the network has been increased in accordance with the number and the lengths of the lines 36 and 44 of metal layer which have been removed, while the capacitance of the network, if the lines 36 and 44 of removed metal layer are narrow, has remained substantially unchanged.

With the distributed network of the invention, a resistance to capacitance (R/C) ratio of 1,000 or more may be readily obtained, where R is the resistance of the network in ohms and C is the capacitance of the network in microfarads. This differs significantly from the R/C ratios of known capacitors wherein it is desired to maximize the capacitance value of the capacitor with respect to the inherent resistance value of the capacitor to obtain an R/C ratio which is generally less than 0.1.

The capacitance value of the'capacitor is determined by the following items: (1 the amount of overlap of the metal layers 24 and 32; (2) the length of the overlapping metal layers; (3) the dielectric constant of the dielectric materials 20 and 28, and (4) thethickness of the dielectric materials 20 and 28. It is to be noted that items (1) and (2) taken together determine the effective plate area of the capacitor. If, as previously stated, the lines of metal layer which are removed are extremely narrow, so that the effective plate area of the capacitor is not significantly reduced, then the capacitance value of the network as fabricated will be essentially equal to the capacitance value which would exist if lines of metal layer were not removed to form the resistance, and the network as formed will be of a minimum size for a given capacitance value.

The value of the resistance is determined by the length of the serpentine path formed by the metal layers after portions thereof have been removed, taken in conjunction with the resistivity, width, and thickness of the serpentine path. Therefore, through the proper selection of dielectric materials, dielectric thickness, resistivity, thickness, length and width of the metal layers, the number and length of lines of metal layer removed from the metal layers, etc., it is possible to obtain an RC network having 'a preselected capacitance and resistance between the end contacts thereof.

For example, assume that it is desired to fabricate the distributed R-C network of the invention having a preselected capacitance value C and resistance value R,. For a particular network forming strip material, the width, resistivity and thickness of the metal layer thereof, as well as the thickness and dielectric constant of the sheet of dielectric material thereof, are known. Given the width of the metal layer, and the thickness and dielectric constant of the dielectric material, the length of each of the two network forming strips required to provide the capacitance value C, in a rolled network may be easily determined. Then, using the length of each network forming strip required to provide the capacitance value C, in a rolled network, and given the resistivity, thickness and width of the metal layer of each network forming strip, the number and the length of the lines of metal layer which must be removed from each network forming strip to provide the resistance value R, in the rolled network may be readily determined. That is, the number and length of lines of metal layer which must be removed from each network strip to form a conductive serpentine path having a particular length and resistance per unit of length, to provide the resistance value R in the rolled network, may be readily determined. The network having the prede termined capacitance value C and resistance value R,

may then be fabricated by winding together the requl'red lengths of network forming strips while simultaneously removing the metal layers along the required number and length of lines, and by then applying a solder block and conductor to each end of the resulting network roll.

It is to be noted that the end to end resistance value of each of the conductive paths formed in the metal layers is R,. However, with an electrical connection at only one end of each conductive path, as in the completed network, the resistance exhibited by each conductive path is R,/2 since since average distance traveled by electrons along the conductive path is one-half of the total length of the path. In the completed network, the resistances of the conductive paths cooperate serially to provide a total network resistance value of R It is also to be noted that the total capacitance value exhibited by the two overlapping but nonconvoluted lengths of metal layers is C /2, the overlapping and convoluted layers exhibiting the total capacitance value C since, in the convoluted form, the area of the overlapping metal layers is doubled.

With another technique for fabricating an R-C network having desired parameters, the required length of each :of two network forming strips, and the required number and length of the lines of metal layer to be removed, to provide the desired capacitance and resistance values, are first determined in accordance with the aforementioned method. In this case, with the metal layer removing devices 112 and 116 actuated to remove the required lines on each of the metal layers 24 and 32, while the network is being wound on the arbor 96, the increasing capacitance value thereof is monitored with a bridge type circuit (not shown) through two sensing probes 136 and 140. As the network is wound, the the sensing probe 136 electrically engages the metal layer 24 through a conductive outer ring 144 of the guide roller 80, which is separated from an inner roller 148 of the guide roller 80 by an insulating material 152, and the sensing probe 140 electrically engages the metal layer 32 of the network forming strip 16 through an outer conductive ring 156 of the guide roller 108, which is separated. from an inner ring 160 by an insulating material 164. When the desired capacitance value is detected by the bridge circuit through the probes 136 and 140, winding of the network roll on the arbor 96 is stopped. Assuming that the dielectric and metal layer properties of the network forming strips 12 and 16 supplied from the reels 76 and 100 remain essentially constant over the entire length of the reels 76 and 100, the R-C network on the arbor 96, the winding of which was terminated when the desired capacitance was detected, will also have the desired resistance. In this manner, successive additional R-C networks may be wound with the apparatus of FIG. 2 to the desired parameters by merely measuring the capacitance value of each network being wound.

The impedance of an R-C network fabricated in accordance with the teachings of the invention may be expressed as Z R j/21rfC, where R and C are the network resistance and capacitance values, respectively, and f is the frequency of the energizing signal applied across the electrical connections to the network. From the relationship Z R j/21rfC, it is seen that as the frequency of the energizing signal increases, the reactance component j/21rrrfC decreases toward zero, until at some frequency value f, the impedance of the network becomes essentially equal to R. Thereafter, for all frequencies above f,, the impedance of the network is essentially constant and equal to R.

While one embodiment of the invention has been described in detail, it is understood that various other modifications and embodiments may be devised by one skilled in the art without departing from the spirit and scope of the invention. For example, while it has been taught that the lines of removed metal layer are very narrow, it is conceivable that for certain purposes it would be desirable to remove the metal layer along relatively wide lines with a resulting loss in capacitance value for a given length of network forming strips. Also, instead of forming a network roll from first and second dielectric sheets, each having a metal layer contiguous to one side thereof, a dielectric material having a metal layer on both sides thereof, the metal layers being electrically isolated one from the other, may be wound with a non-metal coated dielectric material to form a convoluted network roll. In this case, and with appropriate margins formed along the edges of the metal layers, the lines of metal layer on each side of the dielectric sheet may be simultaneously removed by a metal layer removal device.

What is claimed is:

1. In a resistor-capacitor network:

first and second lengths of overlapping and convoluted insulating material;

a first conductive path on a first side of the first length of insulating material, the first path extending back and forth lengthwise along the insulating material in a serpentine fashion;

a second conductive path on a first side of the second length of insulating material, the second path extending back and forth lengthwise along the insulating material in a serpentine fashion, the first side of the second length of insulating material being chosen such that the first and second conductive paths are electrically separated by the first and the second lengths of insulating material;

first means for electrically contacting only one end of the first conductive path, and

second means for electrically contacting only one end of the second conductive path, the first and second conductive paths each forming a resistive path running between the contacted end of the path and the uncontacted end of the path, and together forming a capacitive path therebetween, so that a resistor-capacitor network is formed between the first and second contacting means.

2. In a resistor-capacitor network as recited in claim 1, wherein the electrically contacting means comprises a solder block at each end of the convoluted lengths of insulating material, each solder block contacting an end portion of a different conductive path.

3. In a resistor-capacitor network as recited in claim 1, wherein:

the first and second conductive paths are each a plurality of straight and parallel conductive paths extending lengthwise of the lengths of insulating material and interconnected at their ends to define a serpentine path.

4. In a resistor-capacitor network roll having a frequency dependent impedance, the network exhibiting a first impedance in response to an energizing signal applied thereto having a frequency which approaches zero, and exhibiting a decreasing impedance which approaches an essentially constant value in response to an increasing frequency energizing signal applied thereto:

first and second overlapping, convolutely wound network forming strips, each strip being a sheet of dielectric material having a conductive, metal layer contiguous to one side thereof, the dielectric material of one of the strips separating the metal layer of that strip from the metal layer of the other strip, and each of the metal layers being a conductive path extending back and forth lengthwise along the strip in serpentine fashion;

first means for electrically contacting only one end of the conductive path on the first network forming strip, and

second means for electrically contacting only one end of the conductive path on the second network forming strip, the conductive paths on the first and second network forming strips each forming a resistive path extending between the contacted end of the path and the uncontacted end of the path, and together forming a capacitive path therebetween, so that a resistor-capacitor network is formed between the first and second contacting means.

5. In a resistor-capacitor network:

first and second interleaved, convoluted strips of insulating material forming a roll;

a first flat conductor extending serpentine fashion along a first surface of the first strip of insulating material with the first leg of the serpentine conductor extending along a first lengthwise edge of the first strip of insulating material and with the last leg of the serpentine conductor extending along a path that is spaced from the opposite lengthwise edge of the first strip of insulating material;

a second fiat conductor extending serpentine fashion along a first surface of the second strip of insulating material with the first leg of the serpentine conductor extending along a first lengthwise edge of the second strip of insulating material and with the last leg of the serpentine conductor extending along a path that is spaced from the opposite lengthwise edge of the second strip of insulating material, the first side of the second length of insulating material being chosen such that the first and second flat conductors are electrically separated by the first and second strips of insulating material, and the first lengthwise edge of the second strip of insulating material being that edge which is at the opposite end of the roll from the first lengthwise edge of the first strip of insulating material;

first means for electrically contacting only the first leg of the 'first conductor, and I second means for electrically contacting only the first leg of the second conductor, the first and second conductors each forming a resistive path running between the contacted first leg of the conductor and the uncontacted last leg of the conductor where the resistance is determined by the resistivity, length, width and thickness of the first and second conductors, and together forming a capacitive path therebetween where the capacitance is determined by the total overlapping area of the first and second conductors, taken in conjunction with the thicknessand the dielectric constant of the first and second strips of insulating material. 

1. In a resistor-capacitor network: first and second lengths of overlapping and convoluted insulating material; a first conductive path on a first side of the first length of insulating material, the first path extending back and forth lengthwise along the insulating material in a serpentine fashion; a second conductive path on a first side of the second length of insulating material, the second path extending back and forth lengthwise along the insulating material in a serpentine fashion, the first side of the second length of insulating material being chosen such that the first and second conductive paths are electrically separated by the first and the second lengths of insulating material; first means for electrically contacting only one end of the first conductive path, and second means for electrically contacting only one end of the second conductive path, the first and second conductive paths each forming a resistive path running between the contacted end of the path and the uncontacted end of the path, and together forming a capacitive path therebetween, so that a resistorcapacitor network is formed between the first and second contacting means.
 2. In a resistor-capacitor network as recited in claim 1, wherein the electrically contacting means comprises a solder block at each end of the convoluted lengths of insulating material, each solder block contacting an end portion of a different conductive path.
 3. In a resistor-capacitor network as recited in claim 1, wherein: the first and second conductive paths are each a plurality of straight and parallel conductive paths extending lengthwise of the lengths of insulating material and interconnected at their ends to define a serpentine path.
 4. In a resistor-capacitor network roll having a frequency dependent impedance, the network exhibiting a first impedance in response to an energizing signal applied thereto having a frequency which approaches zero, and exhibiting a decreasing impedance which approaches an essentially constant value in response to an increasing frequency energizing signal applied thereto: first and second overlapping, convolutely wound network forming strips, each strip being a sheet of dielectric material having a conductive, metal layer contiguous to one side thereof, the dielectric material of one of the strips separating the metal layer of that strip from the metal layer of the other strip, and each of the metal layers being a conductive path extending back and forth lengthwise along the strip in serpentine fashion; first means for electrically contacting only one end of the conductive path on the first network forming strip, and second means for electrically contacting only one end of the conductive path on the second network forming strip, the conductive paths on the first and second network forming strips each forming a resistive path extending between the contacted end of the path and the uncontacted end of the path, and together forming a capacitive path therebetween, so that a resistor-capacitor network is formed between the first and second contacting means.
 5. In a resistor-capacitor network: first and second interleaved, convoluted strips of insulating material forming a roll; a first flat conductor extending serpentine fashion along a first surface of the first strip of insulating material with the first leg of the serpentine conductor extending along a first lengthwise edge of the first strip of insulating material and with the last leg of the serpentine conductor extending along a path that is spaced from the opposite lengthwise edge of the first strip of insulating material; a second flat conductor extending serpentine fashion along a first surface of the second strip of insulating material with the first leg of the serpentine conductor extending along a first lengthwise edge of the second strip of insulating material and with the last leg of the serpentine conductor extending along a path that is spaced from the opposite lengthwise edge of the second strip of insulating material, the first side of the second length of insulating material being chosen such that the First and second flat conductors are electrically separated by the first and second strips of insulating material, and the first lengthwise edge of the second strip of insulating material being that edge which is at the opposite end of the roll from the first lengthwise edge of the first strip of insulating material; first means for electrically contacting only the first leg of the first conductor, and second means for electrically contacting only the first leg of the second conductor, the first and second conductors each forming a resistive path running between the contacted first leg of the conductor and the uncontacted last leg of the conductor where the resistance is determined by the resistivity, length, width and thickness of the first and second conductors, and together forming a capacitive path therebetween where the capacitance is determined by the total overlapping area of the first and second conductors, taken in conjunction with the thickness and the dielectric constant of the first and second strips of insulating material. 